There are basically two types of lubricant—oil and grease. Oil has two components: base oil and additives. Grease has three components: base oil, thickener, and additives. Note that oil and grease both share the components of base oil and additives. The difference between an oil and grease is that grease has a thickener. Additives are blended with the base oil to give the oil certain properties such as corrosion resistance or oxidation inhibition. Generally, mineral oil has been employed as base oil in lubricants.
Biodegradable oils are much sought after to replace non-biodegradable mineral oils with increasing awareness of environmental preservations. Two primary classes of biodegradable oils are vegetable oils and synthetics. Vegetable oils offer good biodegradability. Vegetable oils in their natural form lack sufficient oxidative stability. Low oxidative stability means, if untreated, the oil will oxidize rather quickly during use, becoming thick and polymerizing to a plastic-like consistency. Chemical modification of vegetable oils and/or the use of antioxidants can address this problem, but increase the cost. Another negative point to vegetable oils is their high pour point (the temperature at which oil loses fluidity and does not flow). This problem too can be addressed by winterization, addition of chemical additives (pour point suppressants) and/or blending with other fluids possessing lower pour points, but again increase the cost.
Despite their poor oxidative stability, vegetable oils have high viscosity indices, excellent lubricity in extreme pressure, low volatility and good compatibility with additives. Palm oil which originates from Elaeis guineensis possesses all the aforementioned advantages of a vegetable oil. In addition to that, palm oil has better oxidative stability compared to other vegetable oils.
GB patent No. 2,264,305 discloses the use of palm oil liquid fraction derivative, known as palm olein as the base oil to provide a satisfactory lubricant for industrial and automotive requirements. Although palm oil has better oxidative stability compared to other vegetable oils, palm olein is still not the preferred choice to be used as base oil for lubricant as an ester additive is still needed to improve its stability and to prevent crystallization during storage.
U.S. Pat. No. 6,117,827 disclosed a biodegradable base oil of satisfactory low temperature fluidity, oxidative stability, lubricity and of low cloud point. The process for manufacturing the biodegradable base oil is characterized in that hardened palm fractionated oil, high oleic sunflower oil and medium chain triglyceride are mixed and subjected simultaneously to an ester interchange reaction in the presence of an enzymatic catalyst, wherein the enzymatic catalyst is a lipase having a specificity to glyceride positions 1 and 3. Multiple raw materials with stringent requirements are needed for the production of the said biodegradable base oil.
Three most common types of synthetic oils are:                1. Poly-alpha-olefins (PAO)        2. Poly-alkylene glycols (PAG)        3. Ester oilsA major disadvantage of both PAOs and PAGs is their poor solubility with regard to additives. Because the additives themselves must also be biodegradable, this limits the additives that can be used to formulate effective biodegradable lubricants from PAOs and PAGs.        
Ester oils have acquired increasing importance as high quality biodegradable lubricating oils because of its high performance properties and custom design versatility. Ester families commonly used in synthetic lubrication are diesters, polyol esters, monoesters and trimellitates. However, ester oils are normally for high-end usage because of its higher price compared to other synthetic base oils.
U.S. Pat. No. 5,773,391 disclosed a polyol ester suitable for lubricant application. The polyol ester is produced by esterifying an aliphatic or alicyclic polyol containing from 2 to about 10 hydroxyl groups with an aliphatic monocarboxylic acid mixture derived from a high oleic vegetable oil wherein the oleic content is at least 72 percent and the vegetable oil is canola oil, sunflower oil or peanut oil. The esterification reaction is conducted at temperatures in the vicinity of 75° C. to 200° C. for 5 to about 15 or more hours. The condition needed for the esterification reaction is very energy demanding as heating is needed for up to about 15 or more hours.